1. Field of the Invention
The present invention relates to a vane rotary type gas compressor for use in an automotive air conditioning system or the like and, in particular, to a vane rotary type gas compressor improved in terms of vane projectability at the start up of operation of the compressor.
The present invention relates to a vane rotary type gas compressor for use in an automotive air conditioning system or the like and, in particular, to a vane rotary type gas compressor improved in terms of vane projectability at the start up of operation of the compressor.
2. Description of the Related Art
FIGS. 6 through 8 show a conventional vane rotary type gas compressor.
As shown in FIGS. 6 through 8, in this kind of vane rotary type gas compressor, refrigerant gas is introduced into a suction chamber 2 from the piping of an air conditioning system (not shown) through a suction port 2a. The refrigerant gas introduced into the suction chamber 2 is sucked into a cylinder chamber 5 in a cylinder 3 by the torque of a rotor 4 in the cylinder 3 and is compressed therein. The compressed refrigerant gas is discharged into an exhaust chamber 6, stored temporarily therein, and returned to the piping of the system from a discharge port 6a. 
As the structure of a compressor main body 1 will be described specifically. The cylinder 3 with an elliptical inner peripheral surface is equipped with the rotor 4. A plurality of slit-like vane grooves 16 are radially formed in the outer peripheral surface of the rotor 4, and vanes 17 are fitted in the vane grooves 16 so as to be capable of radially projecting and retracting from and into the rotor 4. These vanes 17 are capable of moving toward and away from the inner peripheral surface of the cylinder 3 by the centrifugal force due to the rotation of the rotor 4 and back pressure of vane groove bottom portions 16a, and divide the cylinder chamber 5 defined by the inner peripheral surface of the cylinder 3 and the outer peripheral surface of the rotor 4 into a plurality of compression chambers 5a. 
Further, in the outer periphery of the cylinder 3, there are provided discharge chambers 19 and discharge valves in each discharge chambers. Formed in the inner peripheral surface of the cylinder 3 are cylinder discharge holes 18 establishing communication between the discharge chambers 19 and the cylinder chamber 5. Further, arranged in the front side of the cylinder chamber 5 are suction passages 2b establishing communication between the suction chamber 2 and the cylinder chamber 5. Formed in the cylinder 3 are cylinder suction passages 3a establishing communication between the suction passages 2b and the rear side of the cylinder chamber 5.
The compressor main body 1 is constructed as described above, and the compression chambers 5a defined by the vanes 17 repeatedly undergo changes in volume by rotation of the rotor 4. The refrigerant gas in the suction chamber 2 is sucked into the compression chambers 5a through the suction passages 2b and the cylinder suction passages 3a by the compression chambers 5a, which repeatedly undergo changes in volume. The sucked refrigerant gas is compressed by the compression chambers 5a. After the compression, the refrigerant gas is discharged into the discharge chambers 19 through the cylinder discharge holes 18.
As described above, the gas compressor sucks in and compresses refrigerant gas, so that it necessary to effect lubrication and sealing on plain bearings and other sliding portions, etc. in the compressor main body 1 and on the sliding portions such as the rotor 4 and the vanes 17 and the compression chambers 5a in the cylinder 3, and lubricant is used for that purpose.
Thus, in the compressor main body 1 and the cylinder 3, there is provided a supplying system for supplying lubricant. The lubricant supplying system in the compressor main body 1 and the cylinder 3 will be described. Lubricant is stored in an oil sump 7 formed in the lower portion of the exhaust chamber 6. The lubricant stored in the oil sump 7 is supplied to the various portions mentioned above. More specifically, lubricant is supplied to a plain bearing 9a in the rear side block 9 and a plain bearing 8a in the front side block 8. Further, lubricant is supplied to flat, arcuate grooves 11 formed in the rear side block 9 and the front side block 8 so as to be opposed to the rotor 4 and adapted to communicate with one of the plurality of vane grooves 16 when the rotating angle of the rotor 4 is within a fixed angle range. Further, lubricant is supplied to a high pressure supplying hole 10 formed in the rear side block 9 so as to be opposed to the rotor 4 and adapted to communicate with one of the plurality of vane grooves 16 when the rotating angle of the rotor 4 is within a fixed angle range. Further, lubricant is supplied to the compression chambers 5a and other sliding portions. At this time, the flat groove 11 and the high pressure supplying hole 10 are spaced apart from each other to a degree such that they do not communicate with each other through the vane grooves 16.
Lubricant is supplied to the plain bearing 9a in the rear side block 9 through a first supply passage 12 formed in the rear side block 9 and establishing communication between the oil sump 7 and the plain bearing 9a. Lubricant is supplied to the plain bearing 8a in the front side block through a third supplying passage 13 formed in the rear side block 9, the cylinder 3, and the front side block 8 and establishing communication between the oil sump 7 and the plain bearing 8a. Due to the clearance between the rear side block 9 and the shaft, the lubricant supplied to the plain bearing 9a in the rear side block is supplied to the flat groove 11. Lubricant is supplied to the high pressure supplying hole 10 through the first supplying passage 12 formed in the rear side block 9 and establishing communication between the oil sump 7 and the high pressure supplying hole 10. As stated above, the first supplying passage 12 is branched into the plain bearing 9a side and the high pressure supplying hole 10 side in the rear side block.
In the above-described lubricant supplying system, during operation of the compressor main body 1, the refrigerant gas compressed through the rotation of the rotor 4 is discharged into the exhaust chamber 6 to increase the pressure inside the exhaust chamber 6, with the result that pressure is applied to the surface of the oil sump 7, whereby lubricant is circulated through the supplying passages to effect lubrication or sealing on the sliding portions. Then, the lubricant is mixed into the refrigerant gas inside the cylinder 3, and discharged into the exhaust chamber 6 to return to the oil sump 7 again, thereby circulating through the compressor main body 1 again. See for example, Japanese Patent Publication Number JP 2002-227784 A.
During the operation of the gas compressor described above, the rotor 4 is rotating at a high speed, and the pressure of the exhaust chamber 6 is higher than that in the suction chamber 2 due to the compressed refrigerant discharged into it, with lubricant in the oil sump 7 circulating through the gas compressor and the flat groove 11 also being filled with lubricant. Thus, in the suction/compression process effected by the rotation of the rotor 4, the vanes 17 are pressed against the inner peripheral surface of the cylinder 3 by the centrifugal force due to the high-speed rotation of the rotor 4 and the vane back pressure due to the supply to the vane groove bottom portions 16a of the lubricant in the flat groove 11 communicating with the vane grooves 16. The vanes 17 thus pressed divide the cylinder chamber 5, thereby defining the compression chambers 5a. 
Here, the suction/compression process refers to the process from starting of an increase in the volume of the compression chambers 5a and starting of flowing-in of refrigerant gas into the compression chambers 5a to starting of a reduction in the volume of the compression chambers 5a, with refrigerant gas not having been discharged from the compression chambers 5a yet.
Further, when the refrigerant gas sucking/compressing process has advanced to the stage immediately before discharging refrigerant gas from the compression chambers, the pressure inside the compression chambers 5a is increased by the pressure of the compressed refrigerant gas, and this pressure causes the vanes 17 to be pushed back toward the interior of the vane grooves 16 to be nearly separated from the inner peripheral surface of the cylinder 3. However, at the stage immediately before the discharging of refrigerant gas, the high pressure supplying hole 10 is adapted to communicate with the vane grooves 16, and lubricant at a pressure equal to that in the exhaust chamber 6 is supplied from this high pressure supplying hole 10 to the vane groove bottom portions 16a to add to the vane back pressure. Due to this vane back pressure, the vanes 17 are prevented from being separated from the inner peripheral surface of the cylinder 3 as a result of being pushed back toward the interior of the vane grooves 16.
However, in the conventional gas compressor described above, it can happen that the rotor 4 rotates at a low speed at the start of the compressor, thus causing a shortage of centrifugal force applied to the vanes 17. When the centrifugal force is insufficient, the projectability of the vanes 17 degenerates, so that the vanes 17 are not pressed against the inner peripheral surface of the cylinder 3, which means there is a fear of the cylinder chamber 5 not allowing division into the compression chambers 5a. 
Further, at the start of the compressor, there may be a shortage of pressure in the exhaust chamber 6. Further, it can also happen that the temperature condition is rather severe, that the compressor is left unattended for a long period of time, and that the pressures of the suction chamber 2 and of the exhaust chamber 6 are reversed. In such cases, there will be a shortage of lubricant supplied to the flat groove 11 and a shortage of lubricant supplied to the vane grooves 16, resulting in a reduction in the vane back pressure. In such a case also, the projectability of the vanes 17 will deteriorate due to the reduction in the vane back pressure, so that there is a fear of the vanes 17 not being pressed against the inner peripheral surface of the cylinder, making it impossible to divide the cylinder chamber 5 into the compression chambers 5a. 
When the projectatbility of the vanes 17 thus deteriorates to make it impossible to define the compression chambers 5a, the requisite period of time from the start of the compressor to the stage where the suction/compression of refrigerant gas is possible becomes rather long, thereby deteriorating the compression performance at the start of the gas compressor.